


Happy

by DancerInTheMoonlight



Series: Three's Company [2]
Category: Glee, Supergirl (TV 2015), The Flash (TV 2014)
Genre: Alternate Universe, Alternate Universe - Canon Divergence, Alternate Universe - No Powers, Anal Sex, Bisexual Character, Bisexuality, Crack Crossover, Domestic Fluff, Established Relationship, Fluff and Smut, Multi, My First Smut, Oral Sex, Polyamory, Porn with Feelings, Relationship(s), Sebastian Smythe Has Feelings, Sharing a Bed, Threesome - F/M/M
Language: English
Status: Completed
Published: 2020-08-24
Updated: 2020-08-24
Packaged: 2021-03-06 17:42:30
Rating: Explicit
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 3,262
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/26092813
Author URL: https://archiveofourown.org/users/DancerInTheMoonlight/pseuds/DancerInTheMoonlight
Summary: "Sebastian couldn’t help the smile spreading on his face, thinking he was incredibly lucky. He was happy."
Relationships: Blaine Anderson/Sebastian Smythe, Kara Danvers/Blaine Anderson, Kara Danvers/Sebastian Smythe, Kara Danvers/Sebastian Smythe/Blaine Anderson
Series: Three's Company [2]
Series URL: https://archiveofourown.org/series/1894462
Kudos: 15





	Happy

**Author's Note:**

> So I said it was going to be platonic.  
> And then this happened. With crack and, interestingly enough, some pretty heavy feels.  
> This is set post-Meet The Cute (which I will finish, ofc). 
> 
> Here goes. o_o

Blaine was going over some sheet music while Sebastian was reading the latest sci-fi novel he dug up from Cisco’s impeccable stash, Kara snuggled by his side between them on the bed. It was cozy like that, the three of them making a relaxed constellation of limbs among soft sheets and fluffy pillows. Sebastian glanced at Blaine. His lips were pressed together in concentration and his hand made absent-minded rhythmic motions against his knee. Sebastian couldn’t help the smile spreading on his face, thinking he was incredibly lucky. He was happy.

“You’re staring,” Blaine said, his eyes still glued to the music in his lap.

“And?” Sebastian smirked. “I’m allowed.”

Blaine scoffed but ignored him. Sebastian put his book down and settled against the headboard. He wondered how long he could keep on staring before Blaine cracked and looked back. Not too long, it turned out. Blaine shook his head, smiling, and lifted his eyes towards the ceiling in a ‘heaven help me’ manner. 

“What is it?” he asked, finally looking at Sebastian.

“Nothing. I just like looking at you.” Sebastian gave a lazy shrug and ogled some more. Blaine rolled his eyes but his smile grew bigger.

“You’re ridiculous,” Blaine said, looking like if he was torn between Sebastian and his sheet music. Sebastian reached over and guided him into a less than innocent kiss.

“Get a room,” Kara groaned sleepily against Sebastian’s shoulder and Sebastian chuckled, breaking the kiss.

“We’re already in one,” he grinned at Blaine who just sighed and put his music away. “How great is that?” Sebastian kissed the top of Kara’s head.

“ _Hnn_ ,” she said articulately and rolled onto her back to look up at him. For a second, Sebastian lost himself in sky blue. “I’m kinda tired,” she pouted at him and turned to look at Blaine who just returned her look with a mixture of sympathy and acquiescence, like he could totally get behind the idea of some sleep but also like he’d accepted the fact that he would probably have to get behind Sebastian first in order to get some.

“What if I told you,” Sebastian drew closer in a manner he obviously thought irresistible, even though Kara pressed her lips together like she was trying not to laugh, “that you don’t have to do anything?” He hovered over her and raised his eyebrows for emphatic effect.

“ _Really?_ ”

“Mhm,” Sebastian nuzzled her face and gave her nose a feather-light kiss. “You just lie back and relax, and let me do all the work.”

“ _All_ the work?” Kara smirked up at him she glanced at Blaine, who nodded solemnly, smiling at Sebastian’s antics.

“I’ll do a little work too,” Blaine quipped.

She pretended to think about it.

“Okay,” she said simply, and leaned further against the pillows. Sebastian grinned and pecked her cheek.

“Oh, thank God, I was beginning to worry he was going to have to ‘seduce’ you some more,” Blaine said leaning down and swallowing her laugh and Sebastian’s “ _Hey!_ ” muffled against her neck in a deep kiss.

“Mmm, kisses, I like that,” Kara hummed as Sebastian slid lower and Blaine moved on to her neck to kiss her some more.

“And I think we _all_ know who’s the best kisser here,” Sebastian said while mouthing at some skin under Kara’s t-shirt. “This has to go,” he added tugging on the hem as if the shirt offended him by existing. Kara chortled while Blaine just rolled his eyes and pulled her back into another kiss.

“It’s not a competition, Sebby,” she said when Blaine broke the kiss to help her pull the shirt off.

“What do you mean it’s not a competition?” Sebastian asked with a straight face, even though his eyes twinkled like Christmas had come early. “You mean to tell me that I’m _not_ the best ki— _mmph_ ” he was cut off when Blaine surged forward and tackled his mouth. Sebastian moaned into the kiss.

“Shut up,” Blaine ordered after performing a brief but intense tongue-fucking number on his mouth.

“Yes, sir,” he smirked back, attempting to chase Blaine’s lips further but Blaine turned his attention back to Kara. Sebastian pinched his side as revenge, which made Blaine chuckle into Kara’s cheek and slap his hand away.

“Sebby.”

“I’m sorry, I’ll behave,” he leaned down to kiss her on the mouth. “Or, misbehave,” he said licking into it and biting her lip as his hands travelled to her chest. She sighed softly in approval. He could feel Blaine’s hand travelling down her body in a slow, exploratory caress.

“Nice knicks,” Sebastian heard Blaine’s smug tone and he glanced down where Blaine’s fingers were reaching under the elastic of Kara’s deep blue briefs with a large A in the center.

“Thanks. My boyfriend got them for me,” she smiled dopily at Blaine who smiled back as her breath hitched when his finger started tracing teasing patterns around her core. Blaine got her those briefs.

“ _Nerds_ ,” Sebastian shook his head smiling into her skin. He sucked a kiss just below her right breast making her gasp and arch up toward his mouth. Blaine effectively swallowed any other sounds coming from Kara as his fingers danced between her legs, not quite going where she wanted them most.

“Stop _teasing_ ,” she whined, squeezing the front of Blaine’s sweats and surprising him into a yelp. Sebastian took the opportunity and slid lower, kissing over Kara’s belly down to the bold printed A. He let his teeth graze Blaine’s hand on the way and deliberately swiped his tongue over the inside of Blaine’s wrist, noting how the other shivered with pleasure at the unexpected contact. Beneath Kara’s palm, Blaine was very obviously hard and while Sebastian wasn’t always the one to rush things, he had been sporting a hard-on even before he initiated the whole thing and was too far gone to care whether he’d have Blaine’s hand or his cock, just as long as he was getting some release.

“Yeah, stop teasing,” he peered up at Blaine, quirking his eyebrows like posing a challenge. If his ass happened to be sticking up further in the air than strictly necessary, that was purely coincidental and had nothing to do with him. Blaine pulled him into another kiss, which was far more tongue than anything else, pulling Sebastian’s shirt off along the way. His hands roamed the newly exposed skin in a way Sebastian could lose himself in forever but they retreated all too soon. Pressing one last kiss to Sebastian’s lips and a quick peck to whatever part of Kara was closest in his reach (which happened to be her knee), Blaine stood and headed towards the bathroom.

“I’ll be right back,” he said and Sebastian wasted no time in getting rid of any remaining clothes. He slid off Kara’s _Avengers_ briefs without any further ado and licked a long, sensual stripe from the inside of her knee to her groin. He sucked on a sensitive spot, his tongue doing the same dance as Blaine’s hand before him and she twisted helplessly underneath. Her hands found their way into his hair and she pulled his head back with a grip tight enough to make his smug smirk falter around a moan.

Kara’s eyes were dangerous and dark, as dark as, Sebastian imagined, his own must have been at the moment. He abandoned all plans of further teasing and pressed his mouth against her wet core. Her fingers slipped from Sebastian’s hair as she fell back and became all sighs and deep sounds at the slow, deliberate swipes of his tongue.

Like Sebastian, Kara was a vocal lover, and in that respect, they were eerily similar. Where she liked it slow, he liked it rough – but when it came to vocalizing pleasure, they were in perfect sync. Blaine joked once that they sang sex duets when they were together, and Sebastian spent a grand total of two weeks trying to prove him wrong, which had been an interesting affair in itself, mainly because it proved that the only thing to effectively shut Sebastian up was an elaborate gag. Not that Blaine needed either of them to shut up, he knew. Blaine wasn’t very vocal himself – something Sebastian relished putting to the test, becoming unbearably smug (or so they told him) whenever he succeeded – but the sounds _they_ made were so spontaneous and unaffected it made Blaine’s heart (and his cock) swell with arduous intent, unmatched by anything, except maybe the ardour with which some of their neighbours filed noise complaints. Blaine did have a serious talk with them about that. Kara bit her lips and made an effort to tone it down but Sebastian just went and made up ridiculous noises out of spite, even as he decided straight away to sound-proof the entire apartment. He just hadn’t told Blaine yet.

He didn’t hear Blaine return, but he felt Blaine’s hand caressing his back and kisses trailing up his spine. He came to a halt cloaking Sebastian in his naked body and nipping lightly at Sebastian’s ear, which made his insides jolt with that weird feeling of excitement. “Hi,” Blaine whispered and kissed along his jaw, his hands travelling back down Sebastian’s sides. Sebastian felt Blaine’s cock twitch against his lower back as he pushed a slow finger into Kara and pumped it even slower, crooking the tip upwards on its way out. “Yes, _yes_ ,” she moaned.

“Yeah?” Sebastian was cheeky to reply, but Blaine immediately took the opportunity to busy his mouth with his own. He ground his hips into Sebastian’s ass and Sebastian arched up.

“Don’t tease,” he teased and got a slap on the butt in return. Blaine had no intention to tease, however, and he got up, pulling Sebastian’s hips into a position which left Sebastian between Kara’s legs on his elbows with his backside in the air. The ‘sexy table top’, as Sebastian called it in his head – because the ‘sexy child’s pose’ just sounded deranged.

His lips returned to Kara and he felt Blaine’s hand close around his cock. He stroked, not all too lightly, and it suddenly felt too much.

“Baby, stop,” Sebastian managed, stilling Blaine’s movements with his own free hand. He rested his forehead on Kara’s inner thigh to compose himself.

“What’s wrong?” Blaine sounded concerned as ever, and he could feel Kara’s worried eyes on him without looking.

“Nothing, I. . .” He huffed out a short laugh. “I’m going to come if you keep that up and I _really_ want you to fuck me.”

For all his concern, Blaine snorted at this confession but retracted his hand to a safer spot on Sebastian’s hip. He could feel Kara relax once more.

“Don’t laugh at me, _fuck me_ ,” Sebastian threw him a pointed look and swayed his hips.

“Yes, sir,” Blaine now openly laughed, and Sebastian could imagine Kara’s amused eye roll but he could also hear the blessed sound of the cap popping, so neither of it particularly mattered. Sebastian returned to his expert cunnilingual ministrations, which Kara vocally appreciated. He felt Blaine’s lubed-up fingers tease his entrance and moaned at the sensation, syncing the circles of his tongue to the circular movements he felt on his own skin.

“ _Ah_ , don’t stop,” Kara gasped, trailing a hand through his hair and down the back of his neck. He could feel nails dig into his hairline when he hit a particularly sensitive spot. The pain went south with a force.

“Fingers, please,” he breathed out against Kara pressing backwards impatiently even as his own fingers joined his tongue to pump into her. He hoisted one leg over his shoulder and coiled his free arm around her thigh for better balance.

“Bossy,” Blaine remarked. “Since you said _please_ ,” Blaine indulged him with a slow finger but after that made quick work of building it up to three while Sebastian squirmed in both anticipation and pleasure. Between his fingers and his mouth, Kara was becoming all incoherent sounds. Her hands gripped the bedding like she might float away otherwise.

His movements slowed a bit only when he felt Blaine enter him, devotedly and soundlessly, like he was stepping into consecrated ground. No matter how rough it ultimately got, the beginning always felt like this. Like it was sacred. It made Sebastian believe things.

Blaine set a moderate pace, which Sebastian matched with rhythmic movements of his fingers, wanting so much more and even less, all at the same time. Unabashed by feeling, he let out a deep sound as Blaine slid in and out of him with firmness and ease. Beneath him, Kara trembled.

“Seb— _ah_ ,” she arched her back with a cry. “I’m— —” she trailed off into wordlessness and her legs clamped down on him, shaking uncontrollably as the orgasm hit her body. Sebastian looked up to admire the frenzied dynamic of her hips and breasts and shoulders, like looking over a curious landscape of radiant skin, of dips and curves, her long hair spread out everywhere, locks and wisps like golden sunrays glowing against the pillows. He never wanted to look away, and despite the lack of vocal appreciation, Sebastian knew by the way he picked up his pace that Blaine was glued to the sight, as well. Sebastian moaned encouragements as she clenched around his fingers trailing soothing kisses along her skin. His breath hitched when Blaine brushed a perfect spot and he felt his own body clench.

“YES,” he gasped.

“Good?” Blaine panted, adjusting his grip on Sebastian’s hips. He moved faster and Sebastian buried his face in the soft skin of Kara’s inner thigh.

“ _Yes_ , _yes_ , _yes_ ,” all he could do was sob in response into Kara’s leg as he held on tight. Her hands returned to his head and she carded gentle fingers through his hair, a sweet contrast to the brutal, pounding caress he was receiving on the other end. Blaine’s hips stuttered. Her fingers twisted his hair the tiniest bit and Sebastian’s cock twitched.

Sebastian glanced up to see Kara’s intense eyes locked on Blaine, who was losing his rhythm and rapidly falling apart.

“I can’t—” he whimpered. His hand gripped Sebastian’s cock as he slumped forward and wrapped an arm around his waist. It was the perfect angle Sebastian didn’t even know he needed.

“Oh fuck,” he gasped as his oncoming pleasure took him by surprise, and he was coming after two strokes. “ _Ah_ — _fuck_ , _fuck_ —” Sebastian had never pretended he had less than dirty mouth. Even so, his cursing had less to do with specific taste in coital vocabulary and more to do with the monosyllabic stuff he was able to procure if he happened to be articulate at all. He felt that ‘fuck’ went straight to the point, at any point. He kept jerking as he came, groaning loudly into the space where Kara’s leg joined the rest of her and forgetting all about finishing into his hand, making a mess of the sheets, which he would definitely worry about later. His groans eased into something softer as Blaine coiled around his pliant body and Sebastian reached backwards to wrap his own arm around him in an automatic response. Contrary to popular belief, he liked to feel close.

True to his word, Blaine was not far behind. Upon contact, his movements stilled, his body tightened and he shuddered, biting into Sebastian’s shoulder as he came inside him.

They lay panting for a peaceful moment.

Blaine placed lingering, sweet kisses on the back of his neck. Kara was back to resting against the pillows, her hand on top of his as he stroked little circles into her hip.

“Someone has to get up first,” Blaine said and did so with a last kiss to Sebastian’s shoulder blade. “You made a mess,” he scolded when Sebastian rolled to the side, revealing the darkened and sticky-white stains underneath. “Probably because you knew it wasn’t your turn to wash the sheets.” Kara snorted.

“Mmm I’ll wash them, come back,” Sebastian whined and made grabbing motions at Blaine. He was granted one hand and he kissed it before letting Blaine go. He cuddled up next to Kara.

“Hello,” he greeted with soft kisses.

“Hi,” her eyes smiled as she kissed him back.

Blaine returned clad in black briefs which Sebastian thought did fantastic things for his ass and with wet towels to wipe them down. He did so with gentle efficiency, with almost clinical precision and flopped down on the bed beside them.

“Come here, you,” Kara melted into Blaine’s arms, pulling him into a slow kiss. “My hot boyfriend,” she hummed, trailing her hands down his back and squeezing lower.

“Huh! _Excuse_ me—” Sebastian protested in indignation from where he was spooned against her back, “—how is _he_ the hot one?” even though he totally thought that Blaine was his hot boyfriend, too. “He buys nerdy pants, for god’s sake!” Blaine’s taste in under things covered the entire Avengers collective. He got Sebastian a pair of Marvel themed briefs as well, but he simply refused to wear them. “If he’s the hot one, and you’re the nice, smart one, what does that make me?”

“The bitching one,” they replied in unison and dissolved into giggles. Sebastian huffed.

“I’m just kidding, Sebby, you’re very hot,” Kara twisted to kiss his collarbone. “And it’s not a competition,” she smirked up at him, squeezing his butt.

She got up to retrieve her briefs and donned her t-shirt back on. Kara hated sleeping naked, even in hot weather. Blaine never slept in anything but underwear and Sebastian could make do either way, usually going commando under light pyjama bottoms.

“Could you pass me—oh, thanks!” he said swiftly catching a pair that Kara pulled out of a drawer and threw at him without looking on her way to the bathroom. He pulled them on and looked at Blaine.

“Am I really bitching?”

“The most btichin’ boyfriend in Coast City,” Blaine replied, eyes soft. He loved him. “Except when you’re fishing for compliments,” he added dodging the finger aiming for his side. “Oh, water,” Blaine remembered and got up to get some to put on the nightstand overnight. Sebastian, who rarely woke out of thirst, never saw the point of keeping water by the bedside but Blaine and Kara swore it was necessary. At least it kept them from climbing over Sebastian to take a drink in the middle of the night.

Sebastian got up as well, joining Kara in the bathroom as she finished getting ready for bed. She brushed her hair and he brushed his teeth, drinking some water from the tap (if only Blaine was there to see some sense).

“Braid?” he asked Kara, wiping his mouth. She hummed.

“Okay. But loose.”

Sebastian did a loose braid with quick and expert fingers, and tucked it into the back of her shirt. “All done,” he finished with a kiss on her neck and gazed at her in the bathroom mirror. He loved her. “Let’s go to bed.”

When they got back, Blaine was already tucked in, lights out, water in place, one for Kara on the other side. Blaine almost never slept in the middle, but both Kara and Sebastian frequently did. Sebastian flopped in the middle, settling onto his back and both of his partners, his friends, his lovers pulled closer. He felt Kara’s arm around his waist, Blaine’s hand along his chest, their tangle of legs and soft breaths. He loved them.

“I love you both so much,” he whispered into darkness.

He was happy.

**Author's Note:**

> Fun fact, I have no idea how to write smut and this makes me pretty anxious. But it's fine. I am not sorry.  
> If you find this ship weird, that is also fine. :) Cheers.


End file.
